The exercise used for bicep development and strengthening is the curling exercise, using a barbell or dumbells. The palms up supine hand position during the curling exercise is the key factor in the development of the bicep brachii, also known as the upper arm or just the biceps.
Prior to this invention the standard straight barbell and dumbells were best for the curling exercise, because, the bar for gripping is straight. If the hands are not held in a supine position during the curling exercise the biceps are not fully engaged in the exercise.
The problem that has plagued bodybuilders and weightlifters while doing the curling exercise with the straight barbell or dumbell is, the severe strain on the hands, wrist, and forearm muscles. The cause of this straining is, while curling, the center of gravity is centered on the supined palms of the hands. Therefore the hand, wrist, and forearm muscles are straining to hold the barbell parallel with the forearm. To do the exercise properly one has had to endure this wrist strain. The wrist straining problem with the standard straight barbell and dumbell has given rise to some novel devices to relieve the strain. These devices have basic flaws in their design, that have proved them impracticable for bicep development and strengthening. The most common flaw with these devices is that they try to relieve wrist strain by taking the hands out of supine position, which, in turn, diminishes the effective contraction of the bicep brachii. This defeats the purpose of the curling exercise.